res_remb_modifier: Add module for controlling REMB from CLI.
authorJoshua Colp <jcolp@digium.com>
Thu, 20 Sep 2018 09:48:38 +0000 (09:48 +0000)
committerJoshua Colp <jcolp@digium.com>
Thu, 20 Sep 2018 09:55:32 +0000 (04:55 -0500)
This adds a module which registers a CLI command that can set the
REMB bitrate value for REMB as it enters or exits Asterisk. This
allows you to ignore what Asterisk or a client produces and is
useful for demonstrations.

This does not generate REMB frames, however, but just modifies
them as they flow to or from a channel.

Change-Id: Ib089427c46a4a36d645cecfe02406adb38c17bec

res/res_remb_modifier.c [new file with mode: 0644]

diff --git a/res/res_remb_modifier.c b/res/res_remb_modifier.c
new file mode 100644 (file)
index 0000000..1e79b83
--- /dev/null
@@ -0,0 +1,225 @@
+/*
+ * Asterisk -- An open source telephony toolkit.
+ *
+ * Copyright (C) 2018, Digium, Inc.
+ *
+ * Joshua Colp <jcolp@digium.com>
+ *
+ * See http://www.asterisk.org for more information about
+ * the Asterisk project. Please do not directly contact
+ * any of the maintainers of this project for assistance;
+ * the project provides a web site, mailing lists and IRC
+ * channels for your use.
+ *
+ * This program is free software, distributed under the terms of
+ * the GNU General Public License Version 2. See the LICENSE file
+ * at the top of the source tree.
+ */
+
+/*!
+ * \file
+ *
+ * \brief REMB Modifier Module
+ *
+ * \author Joshua Colp <jcolp@digium.com>
+ */
+
+/*** MODULEINFO
+       <support_level>extended</support_level>
+       <defaultenabled>no</defaultenabled>
+ ***/
+
+#include "asterisk.h"
+
+#include "asterisk/module.h"
+#include "asterisk/cli.h"
+#include "asterisk/channel.h"
+#include "asterisk/framehook.h"
+#include "asterisk/rtp_engine.h"
+
+struct remb_values {
+       /*! \brief The amount of bitrate to use for REMB received from the channel */
+       unsigned int receive_bitrate;
+       /*! \brief The amount of bitrate to use for REMB sent to the channel */
+       unsigned int send_bitrate;
+};
+
+static void remb_values_free(void *data)
+{
+       ast_free(data);
+}
+
+static const struct ast_datastore_info remb_info = {
+       .type = "REMB Values",
+       .destroy = remb_values_free,
+};
+
+static struct ast_frame *remb_hook_event_cb(struct ast_channel *chan, struct ast_frame *frame, enum ast_framehook_event event, void *data)
+{
+       struct ast_rtp_rtcp_feedback *feedback;
+       struct ast_datastore *remb_store;
+       struct remb_values *remb_values;
+
+       if (!frame) {
+               return NULL;
+       }
+
+       switch (event) {
+       case AST_FRAMEHOOK_EVENT_READ:
+       case AST_FRAMEHOOK_EVENT_WRITE:
+               break;
+       case AST_FRAMEHOOK_EVENT_ATTACHED:
+       case AST_FRAMEHOOK_EVENT_DETACHED:
+               return frame;
+       }
+
+       /* We only care about REMB frames, all others will be unmodified */
+       if (frame->subclass.integer != AST_RTP_RTCP_PSFB) {
+               return frame;
+       }
+
+       feedback = frame->data.ptr;
+       if (feedback->fmt != AST_RTP_RTCP_FMT_REMB) {
+               return frame;
+       }
+
+       remb_store = ast_channel_datastore_find(chan, &remb_info, NULL);
+       if (!remb_store) {
+               return frame;
+       }
+       remb_values = remb_store->data;
+
+       /* If a bitrate override has been set apply it to the REMB Frame */
+       if (event == AST_FRAMEHOOK_EVENT_READ && remb_values->receive_bitrate) {
+               feedback->remb.br_mantissa = remb_values->receive_bitrate;
+               feedback->remb.br_exp = 0;
+       } else if (event == AST_FRAMEHOOK_EVENT_WRITE && remb_values->send_bitrate) {
+               feedback->remb.br_mantissa = remb_values->send_bitrate;
+               feedback->remb.br_exp = 0;
+       }
+
+       /* The mantissa only has 18 bits available, so while it exceeds them we bump
+        * up the exp.
+        */
+       while (feedback->remb.br_mantissa > 0x3ffff) {
+               feedback->remb.br_mantissa = feedback->remb.br_mantissa >> 1;
+               feedback->remb.br_exp++;
+       }
+
+       return frame;
+}
+
+static char *handle_remb_set(struct ast_cli_entry *e, int cmd, struct ast_cli_args *a)
+{
+       struct ast_channel *chan;
+       unsigned int bitrate;
+       struct ast_datastore *remb_store;
+       struct remb_values *remb_values;
+       struct ast_framehook_interface interface = {
+               .version = AST_FRAMEHOOK_INTERFACE_VERSION,
+               .event_cb = remb_hook_event_cb,
+       };
+
+       switch(cmd) {
+       case CLI_INIT:
+               e->command = "remb set {send|receive}";
+               e->usage =
+                       "Usage: remb set {send|receive} <channel> <bitrate in bits>\n"
+                       "       Set the REMB value which overwrites what we send or receive\n";
+               return NULL;
+       case CLI_GENERATE:
+               return ast_complete_channels(a->line, a->word, a->pos, a->n, 3);
+       }
+
+       if (a->argc != 5) {
+               return CLI_SHOWUSAGE;
+       }
+
+       if (sscanf(a->argv[4], "%30d", &bitrate) != 1) {
+               ast_cli(a->fd, "%s is not a valid bitrate in bits\n", a->argv[4]);
+               return CLI_SUCCESS;
+       } else if (strcasecmp(a->argv[2], "send") && strcasecmp(a->argv[2], "receive")) {
+               ast_cli(a->fd, "%s is not a valid direction for REMB\n", a->argv[2]);
+               return CLI_SUCCESS;
+       }
+
+       chan = ast_channel_get_by_name(a->argv[3]);
+       if (!chan) {
+               ast_cli(a->fd, "%s is not a known channel\n", a->argv[3]);
+               return CLI_SUCCESS;
+       }
+
+       ast_channel_lock(chan);
+
+       remb_store = ast_channel_datastore_find(chan, &remb_info, NULL);
+       if (!remb_store) {
+               int framehook_id;
+
+               framehook_id = ast_framehook_attach(chan, &interface);
+               if (framehook_id < 0) {
+                       ast_cli(a->fd, "Could not attach framehook for modifying REMB\n");
+                       ast_channel_unlock(chan);
+                       ast_channel_unref(chan);
+                       return CLI_SUCCESS;
+               }
+
+               remb_values = ast_calloc(1, sizeof(*remb_values));
+               if (!remb_values) {
+                       ast_cli(a->fd, "Could not create a place to store provided REMB value\n");
+                       ast_framehook_detach(chan, framehook_id);
+                       ast_channel_unlock(chan);
+                       ast_channel_unref(chan);
+                       return CLI_SUCCESS;
+               }
+
+               remb_store = ast_datastore_alloc(&remb_info, NULL);
+               if (!remb_store) {
+                       ast_cli(a->fd, "Could not create a place to store provided REMB value\n");
+                       ast_framehook_detach(chan, framehook_id);
+                       ast_channel_unlock(chan);
+                       ast_channel_unref(chan);
+                       ast_free(remb_values);
+                       return CLI_SUCCESS;
+               }
+
+               remb_store->data = remb_values;
+               ast_channel_datastore_add(chan, remb_store);
+       } else {
+               remb_values = remb_store->data;
+       }
+
+       if (!strcasecmp(a->argv[2], "send")) {
+               remb_values->send_bitrate = bitrate;
+       } else if (!strcasecmp(a->argv[2], "receive")) {
+               remb_values->receive_bitrate = bitrate;
+       }
+
+       ast_channel_unlock(chan);
+       ast_channel_unref(chan);
+
+       ast_cli(a->fd, "Set REMB %s override to a bitrate of %s on %s\n", a->argv[2], a->argv[3], a->argv[4]);
+
+       return CLI_SUCCESS;
+}
+
+static struct ast_cli_entry remb_cli[] = {
+       AST_CLI_DEFINE(handle_remb_set, "Set the REMB value which overwrites what is sent or received"),
+};
+
+static int load_module(void)
+{
+       ast_cli_register_multiple(remb_cli, ARRAY_LEN(remb_cli));
+       return AST_MODULE_LOAD_SUCCESS;
+}
+
+static int unload_module(void)
+{
+       ast_cli_unregister_multiple(remb_cli, ARRAY_LEN(remb_cli));
+       return 0;
+}
+
+AST_MODULE_INFO(ASTERISK_GPL_KEY, AST_MODFLAG_DEFAULT, "REMB Modifier Module",
+       .support_level = AST_MODULE_SUPPORT_EXTENDED,
+       .load = load_module,
+       .unload = unload_module,
+);